When a close friend of Helen Mirren collapsed and nearly died after he had a cardiac arrest at a film premiere last autumn, the news was kept from her until the night was over.

But once the actress heard how Chris Worwood had been saved by volunteer medics, she vowed to do all she could to make sure other people survive.

Today she was asking members of the public to learn the cardiopulmonary resuscitation skills that can be the difference between life and death.

Dame Helen also wants defibrillators — which deliver electric shocks to the heart — to be more widely available, particularly in schools. “I couldn’t believe that 260 children a year in this country die of cardiac arrest because they have a heart condition nobody knew about,” she said.

And she has become patron of the Voluntary Responder Group, which has 75 volunteers, including staff from RAF Northolt who give their time to act as first response units for the London Ambulance Service.

Volunteer Alan “Al” Moore, a police constable with the Met, spotted Mr Worwood “bright blue and lifeless” on the floor at The Debt premiere at the Curzon Mayfair and began CPR while a defibrillator was brought from the Tube. Dame Helen, 66, could not be more grateful. “It’s very simple. These people saved my friend’s life. In 10 or 15 minutes, he would have been dead if he had not had the fortune of Al being there. I just want more people to have this fortune,” she said.

“It’s not a huge thing. Defibrillators are not expensive. CPR is not difficult — I was taught how to do it this morning. There are skills we should all learn.”

The VRG needs two more cars, costing £50,000, and more volunteers to join a force of 750 who work in their own community. The volunteers attend about 28,000 incidents a year.

Mr Worwood, 40, of Balham, is a TV picture publicity manager who met Dame Helen when she was making Elizabeth I and then researched her photographic autobiography. He said the cause of his cardiac arrest was still not known but he is fine. “If one person reading this article then helps save someone having a cardiac arrest because they know what to do, it would be amazing,” he said.